Evidence for regional catecholamine uptake and storage sites in the transplanted human heart by positron emission tomography.

Positron emission tomography in combination with the newly introduced catecholamine analogue [11C]hydroxyephedrine ([11C]HED) enables the noninvasive delineation of sympathetic nerve terminals of the heart. To address the ongoing controversy over possible reinnervation of the human transplant, 5 healthy control subjects and 11 patients were studied after cardiac transplant by this imaging approach. Regional [11C]HED retention was compared to regional blood flow as assessed by rubidium-82. Transplant patients were divided into two groups. Group I had recent (less than 1 yr, 4.4 +/- 2.3 mo) surgery, while group II patients underwent cardiac transplantation more than 2 yr before imaging (3.5 +/- 1.3 yr). [11C]HED retention paralleled blood flow in normals, but was homogeneously reduced in group I. In contrast, group II patients revealed heterogeneous [11C]HED retention, with increased uptake in the proximal anterior and septal wall. Quantitative evaluation of [11C]HED retention revealed a 70% reduction in group I and 59% reduction in group II patients (P less than 0.001). In group II patients, [11C]HED retention reached 60% of normal in the proximal anterior wall. These data suggest the presence of neuronal tissue in the transplanted human heart, which may reflect regional sympathetic reinnervation.

Lymphoscintigraphy in melanoma: initial evaluation of a low protein dose monoclonal antibody cocktail.

A low protein dose (73 +/- 10 micrograms total) 131I-labeled monoclonal antibody cocktail made of equal microgram quantities of 225.28S (IgG2a) and 763.24T (IgG1) murine monoclonal antibodies, which bind additively to a high molecular weight antigen of melanoma, was evaluated as a lymphoscintigraphic agent in 17 patients with intermediate to thick (mean Breslow depth, 3.39 +/- 0.64 mm) melanomas or clinical Stage II disease scheduled for nodal dissection. Eleven of the patients were clinically Stage I while 6 were clinically Stage II. 131I antibody cocktail, 258 +/- 10 microCi, was administered s.c. at the site of the primary melanoma or its scar following surgical removal. In eight patients, 63 +/- 8 microCi of 125I nonspecific normal sheep IgG was coadministered s.c. Gamma camera imaging was conducted beginning immediately after and continuing for several days following injection. Surgical resection, weighing, and gamma counting of the draining lymph nodes were undertaken in all patients. On gamma scans, early nodal uptake of antibody was most pronounced and of longest duration in the tumor pathologically positive patients (5 of 7 had visible nodal uptake, 4 of 7 visually stable or rising with time), with the t 1/2 of nodal clearance by gamma scan significantly (P less than 0.05) longer than in the negative patients in whom 4 of 10 showed some, although generally transient (0 of 10 stable or rising), nodal uptake. Scans were not easily interpretable when the injection site was very near the draining nodal group, in part due to the detection of scatter activity from the injection site. In several instances the scan was correct and the clinical examination was incorrect as regards nodal disease. Quantitative analysis of the surgically excised draining nodes showed significantly (P less than 0.001) more 131I anti-melanoma antibody uptake in the 21 tumor-involved nodes [0.01217% injected dose (ID)/node median] than in the 512 tumor-negative nodes (0.00051% ID/node median). Median percentage ID/g of anti-melanoma antibody in tumor-involved nodes was significantly greater (P less than 0.01) than in tumor-negative nodes (0.01984 versus 0.003215% ID/g). 125I-labeled nonspecific antibody did not accumulate significantly more in the tumor-involved nodes on a per node or per g basis in the 283 of 533 nodes studied using the dual-label approach (0.0036 versus 0.00092% ID/g). These data demonstrate that by external imaging and by tissue counting that a radiolabeled anti-melanoma monoclonal antibody cocktail can specifically accumulate to melanoma-involved lymph nodes following s.c. administration.(ABSTRACT TRUNCATED AT 400 WORDS)

Calculating radiation absorbed dose for pheochromocytoma tumors in 131-I MIBG therapy.

A protocol for calculating radiation absorbed dose to pheochromocytoma tumors during treatment with 131I-labeled metaiodobenzylguanidine (MIBG) is described. The technique calls for (a) obtaining tumor volumes from Computed Tomography and/or Magnetic Resonance Imaging, (b) computing energy absorbed by assuming complete beta-particle absorption and a standard shape for gamma-ray absorption and (c) scaling from tracer to therapy dose rate by the ratio of administered activities. Also a 131I time-activity curve is obtained from planar, Anger-camera, conjugate-view images of the tumor and a known-strength source, both over a series of days. In addition, to correct for any systematic errors in the calculated uptakes, a larger activity of 123I MIBG is administered separately and quantitative Single Photon Emission Computed Tomography (SPECT) is undertaken. A known-strength source also undergoes SPECT to calibrate the tomograms. Correction for Compton scattering is accomplished by the dual-energy-window technique. The subtraction fraction was found to be 0.7 for the 1/2" crystal camera and the mean reduction in tumor counts for seven tumors from Compton correction was 0.76. The normalization factor needed to bring the conjugate-view activities into agreement with the SPECT values ranged from 0.74 to 1.06. A test study on an anthropomorphic phantom indicated that the error in resultant activities might be estimated as +/- 13%. Application of the protocol led to the calculation of real, or potential (when decision was finally made to not administer therapy) radiation absorbed dose to seven tumors in three patients from an administration of about 8 GBq of MIBG. For two metastatic tumors in a 19-year old patient who did not have her primary cancer resected, the calculated radiation absorbed dose was 170 and 180 Gy. For the four metastatic deposits evaluated in two older patients, both of whom had their primary tumor surgically removed, the values ranged from 18 to 31 Gy.

Labetalol reduces iodine-131 MIBG uptake by pheochromocytoma and normal tissues.

Iodine-131 metaiodobenzylguanidine [131I]MIBG has proven to be an effective radiopharmaceutical for the scintigraphic localization of pheochromocytomas. Uptake of MIBG is inhibited by blockade of the neuronal uptake pathway for catecholamines ("uptake-1") and by depletion of catecholamine storage vesicle contents, but is not significantly affected by conventional alpha- and beta-adrenoreceptor blocking drugs. Labetalol is an antihypertensive agent with combined alpha- and beta-blocking properties that has been used to manage patients with suspected pheochromocytomas. We report eight patients in whom concurrent or recent therapy with labetalol significantly reduced the uptake of [131I]MIBG into salivary glands, liver, spleen, and general body background. Tumor uptake of MIBG was also reduced in two of the three patients who were proven to have pheochromocytomas. In one case, the effect of labetalol persisted for 36 hr after the drug had been discontinued. The inhibitory effect of labetalol on MIBG uptake in sympathomedullary tissues is likely to be a result of the drug's little-known, additional properties of uptake-1 blockade and depletion of storage vesicle contents, rather than its alpha- or beta-blocking effects. Additionally, labetalol would also appear to hasten clearance of MIBG from other tissues. Labetalol therapy should be discontinued for several days (possibly up to 1 wk) before undertaking [131I]MIBG scintigraphy. A comprehensive list of drugs that should be avoided in patients undergoing MIBG scintigraphy is appended.

An analysis of "ablation of thyroid remnants" with I-131 in 511 patients from 1947-1984: experience at University of Michigan.

Between January 1947 and June 1983, 511 patients were given treatment doses of I-131 after surgery for thyroid cancer in the presence of I-131 uptake in thyroid remnants. Thirty-four patients were removed from the study leaving 462 patients with a 99% follow-up at 1 or more yr, with a mean follow-up of 15 yr. Of 267 patients with radioiodine uptake confined to the thyroid bed, 233 (87%) had ablation from the first dose of I-131 ranging from 100 to greater than 200 mCi. The higher the percent uptake, the more difficult it was to achieve ablation. In the percentages of successful ablation, there were no significant differences between I-131 doses of: 100-149 mCi, 150-174 mCi, 179-199 mCi, and 200 mCi or more. The 100-149 mCi ablative dose may furnish "adjuvant" therapy for occult metastases.

Iodine-131 metaiodobenzylguanidine scintigraphy for the location of neuroblastoma: preliminary experience in ten cases.

Ten patients with histologically proven neuroblastoma were studied by [131I]MIBG scintigraphy. Tumor uptake of the radiopharmaceutical showed a spectrum varying from no uptake in one case, to slight uptake in two, moderate uptake in two and intense uptake in five cases. Iodine-131 MIBG scintigraphy was more effective in demonstrating the extent of neuroblastoma spread than were conventional bone scan and CT in one patient, equal to these modalities in four cases, almost equal in two cases and significantly inferior in three cases. These preliminary results suggest that [131I]MIBG scintigraphy is useful in detecting the presence and delineating the distribution of neuroblastoma and may, in certain cases, have therapeutic potential.

Phosphorus-32 therapy of cystic Grade IV astrocytomas: technique and preliminary application.

Instillation of [32P]chromic phosphate to cystic brain tumors was performed in six patients. Three patients had craniopharyngioma, two had Grade IV astrocytoma and one had Grade II astrocytoma. The cyst volumes ranged from 2 to 44 cc. A calculated dose of 20,000 rad was delivered to the cyst wall. The [32P]chromic phosphate dose given to achieve this dose ranged from 0.11 mCi to 2.5 mCi. Radionuclide leakage was not detected in either the central nervous system or the reticuloendothelial system by bremsstrahlung scanning. Stereotactic instillation was done in some cases, others had indwelling catheters. The frequency of cyst fluid aspiration in the three patients with craniopharyngioma decreased postinstillation. In the two patients with Grade IV astrocytoma, reductions in both the CT documented cyst size as well as the frequency of cyst aspiration were noted. We conclude that [32P]chromic phosphate installation by stereotactic or indwelling catheter method is a safe and helpful procedure in the management of cystic brain tumors.

Metaiodobenzylguanidine to map scintigraphically the adrenergic nervous system in man.

Metaiodobenzylguanidine (MIBG) localizes in adrenergic neurons; MIBG labeled with 123I then serves as an analog of norepinephrine, and concentrations of [123I]MIBG reflect sites of adrenergic neurons in organs. Movements of [123I]MIBG into and out of organs were measured by quantitative scintigraphy in man. We perturbed adrenergic neuron function in several ways, and [123I]MIBG concentrations in the heart were subsequently altered in patterns consistent with the concept that [123I]MIBG resides mostly in adrenergic neurons. Uptake of [123I]MIBG into the heart was inhibited by the tricyclic drug, imipramine, and this agent also accelerated the rate of loss of [123I]MIBG. Phenylpropanolamine, a sympathomimetic drug that acts by displacing norepinephrine from neurons, increased the rates of loss of [123I]MIBG from the heart. Exercise was followed by a movement of [123I]MIBG into blood and urine. Generalized autonomic neuropathies were associated with marked diminutions of [123I]MIBG uptake into the heart. We conclude that quantitative scintigraphy in patients will enable determinations of regional disturbances in integrity (by measuring uptake of [123I]MIBG) and function (by measuring rates of loss of [123I]MIBG) of the adrenergic nervous system in the heart.

Iodine-125-MIBG to treat neuroblastoma: preliminary report.

Three children with Stage III neuroblastoma were treated with [125I]MIBG in a phase I toxicity study. Concepts of the treatment were: in small tumors, the absorbed dose of radiation from MIBG labeled with 131I is reduced but the absorbed dose from [125I]MIBG is less affected; and many recurrences of neuroblastoma arise from small tumors. Two patients exhibited only modest thrombocytopenia and leukopenia, the most sensitive indices of radiation toxicity, after receiving 261 and 407 mCi, and 83 and 104 rad of whole-body radiation. One patient died of progressive neuroblastoma; the other two patients have stable disease over 30 mo after treatment. Per millicurie given, [125I]MIBG imparts about one-fourth the radiation dose of [131I]MIBG to the whole body. Iodine-125-MIBG can be given in doses that impart over 100 rad of whole-body radiation and that exceed 400 mCi before toxicity becomes limiting, even in small children.

Effect of angiotensin II on human vascular smooth muscle cell growth.

Inhibitors of the production of endogenous angiotensin II (A-II) can diminish the hyperplastic response produced by arterial injury in animals; however, a similar effect in humans has not been observed. To explain this discrepancy, we compared the effect of A-II on rat aortic smooth muscle cells (R-SMC) and smooth muscle cells derived from human saphenous veins (H-SMC). A-II (10-1000 nM) significantly increased the proliferative rate of R-SMC incubated in 10% serum, but a similar effect was not observed with H-SMC. Incubation of R-SMC for 24 hr with A-II (1 microM) produced a significant increase in cell size (7%) and protein production (18%), whereas no hypertrophic response was noted in H-SMC exposed to A-II. In neither R-SMC nor H-SMC did A-II, in any concentration, induce cell migration. Stimulation of R-SMC with A-II resulted in tyrosine phosphorylation of five proteins (approximately 120, approximately 108, approximately 68, 45, 42 kDa). The 42- and 45-kDa proteins, which we have previously identified as mitogen-activated protein kinases (MAP-K), remained phosphorylated for 1 hr. In H-SMC, only MAP kinases were tyrosine phosphorylated, but with less intensity than in R-SMC, and only for 20 min. In protein kinase C-depleted SMC, tyrosine phosphorylation of MAP kinase was inhibited in both cell types. A-II produced hypertrophy and hyperplasia of R-SMC, but not H-SMC. Differences in intracellular signaling might account for these disparate effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Requirement for protein kinase C activation in basic fibroblast growth factor-induced human endothelial cell proliferation.

The intracellular signaling mechanisms that mediate basic fibroblast growth factor (bFGF)-induced angiogenesis have not been fully identified. In particular, whether activation of the intracellular enzyme protein kinase C (PKC) is necessary or sufficient for bFGF-induced mitogenesis of human endothelial cells is not clear. Accordingly, the effect of bFGF stimulation on the Ca2+ increase and PKC activity of normal human endothelial cells (HEC) was studied, as was the effect of inhibition of PKC and the distribution of PKC isoenzymes in these cells. The addition of bFGF to cultured HEC increased overall PKC activity in the absence of an increase in intracellular Ca2+ and markedly stimulated their proliferation, as did the addition of PKC-activating phorbol esters. bFGF-induced proliferation was prevented by the PKC inhibitors chelerythrine and H-7 and by downregulation of PKC after prolonged incubation with phorbol esters. In contrast, these inhibitors did not prevent HEC proliferation induced by epidermal growth factor. Because of the failure of bFGF to increase Ca2+, we determined whether bFGF-induced proliferation could be mediated by novel or atypical PKC isoenzymes (which are not regulated by Ca2+). Investigation of the isoenzyme distribution of confluent and subconfluent HEC by immunoblotting, Northern transfer analysis, and polymerase chain reaction of reverse-transcribed RNA revealed the presence of several novel and atypical isoenzymes (PKC-delta, -eta, -theta, and -zeta) as well as small amounts of the conventional (Ca(2+)-regulated) isoenzymes PKC-alpha and -beta. Activation of PKC by bFGF, in the absence of an increase in intracellular Ca2+, suggests that one or more of these Ca(2+)-independent PKC isoenzymes are both necessary and sufficient for HEC proliferation after bFGF.

Treatment of neuroblastoma with [125I]metaiodobenzylguanidine.

To find a treatment that may be effective against micrometastases of advanced, stage III or IV neuroblastoma, [125I]metaiodobenzylguanidine (125I-MIBG) was used in a phase I toxicity trial. In seven patients, thrombocytopenia was encountered with absorbed whole body doses of 85-135 rad from 125I-MIBG, but the dosimetry was imprecise in predicting bone marrow injury. Three patients survived for over one year, results that may indicate efficacy of 125I-MIBG therapy.

Clinical experience with Tc-99m labeled (N2S2) anti-melanoma antibody fragments and single photon emission computed tomography.

We evaluated the imaging capability of murine Tc-99m-labeled antimelanoma Fab fragments in 12 patients with clinical stage II and III melanoma. Tc-99m-NRX118.7 antimelanoma Fab fragment, 10.0 to 27.2 mCi (370-1, 006 MBq), was injected IV 30 min after irrelevant nonspecific intact antibody and 5 min after intact specific antibody were given. In all patients, whole-body scans and spot views were obtained. Single photon emission computed tomography (SPECT) was additionally performed in eight of the patients. The procedure was well tolerated, and 31 of 38 known foci of melanoma were detected (sensitivity, 82%). SPECT aided in detecting and better localizing lesions in the head, neck, and chest. The specificity of the technique was satisfactory when interpretation was performed with a knowledge of normal sites of accretion and excretion of technetium-99m activity such as the kidneys and gut. In several instances, lesions were discovered by means of the antibody scan before detection by other methods, and in two instances, the lack of visualization on antibody scan of a palpable mass correctly indicated that no melanoma was present in the mass. Scan results in three patients led to alterations in patient care; including preventing aggressive surgical and nonsurgical treatments. Although these data are encouraging, evaluation in additional patients will be essential to determine the clinical utility of this antibody scan in the management of patients with melanoma.

Radiolabeled meta-iodobenzylguanidine and the adrenergic neurons of salivary glands.

The handling of radiolabeled meta-iodobenzylguanidine (MIBG) by salivary glands was evaluated. In the submaxillary glands of rats, the uptake of 125I-MIBG was decreased after 1) nerve injury induced by 6-hydroxydopamine, 2) inhibition of the uptake-1 pathway by desmethylimipramine, and 3) surgical denervation. However, the reduction in 125I-MIGB uptake was less than that of 3H-norepinephrine (3H-NE) and of the endogenous content of NE in the glands. Yet, the sympathomimetic phenylpropanolamine displaced about the same fraction of 125I-MIBG as 3H-NE. These results suggest that 40% or more of 125I-MIBG resides in extraneuronal sites but that at least 30% and possibly more lies in the adrenergic nerve terminals. Fasting and feeding rats produced changes in the rates of disappearance of 125I-MIBG and 3H-NE from the submaxillary gland that were different, and the rates of loss of 125I-MIBG cannot be used as an index of adrenergic nerve activity. In man, the concentrations of 123I-MIBG in the salivary glands, particularly the parotid gland, are readily visible and measureable. Imipramine reduced the uptake of 123I-MIBG into parotid glands little or not at all; some of the 123I-MIBG may enter neurons via an imipramine-insensitive pathway, but a substantial fraction probably arrives in intraneuronal locations. Thus, phenylpropanolamine displaced over 50% of the parotid pool of 123I-MIBG. However, in only the most severe case of generalized autonomic neuropathy was the uptake of 123I-MIBG reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Toxicity from treatment of neuroblastoma with 131I-meta-iodobenzylguanidine.

Toxic effects from 131I-meta-iodobenzylguanidine (131I-MIBG) treatments of neuroblastoma in six patients were recorded. The toxicity was largely confined to the hematologic system where circulating leukocytes and platelets regularly declined after each dose of 131I-MIBG; the values reached nadirs between three and seven weeks and recovered slowly over subsequent weeks. Prior bone marrow transplantation and infiltration of bone marrow by neuroblastoma appeared to make the hematologic system more vulnerable to the radiation. Dosimetry revealed greater absorbed radiation by the whole body than by the blood and bone marrow. These observations are explained by a relatively rapid exit of 131I-MIBG from the blood to other tissues (but not to the bone marrow). Since treatment of an aggressive and lethal tumor such as neuroblastoma should be pushed to a degree of toxicity, careful dosimetry in each case will be necessary as a guide to reach the point of maximally tolerable toxicity.